a. Field of the Invention
The present invention relates generally to a system and method for navigating an ultrasound catheter to image a beating heart. More particularly, the present invention relates to the coordination of catheter position data with ultrasound imaging data imaging a heart via ultrasound.
b. Background Art
Using ultrasound to image the interior of a beating heart is a known technique. A series of patents (U.S. Pat. No. 5,345,940, issued Sep. 13, 1994; U.S. Pat. No. 6,544,187, issued Apr. 8, 2003; U.S. Pat. No. 5,713,363, issued Feb. 3, 1998) to Seward et al. describe the intra-cardiac ultrasound echo (ICE) technique and are incorporated herein, in their entirety, by reference. According to this technique, an ultrasonic transducer is situated at a distal end of a catheter that is positioned in a heart chamber. The transducer vibrates in response to a control signal to generate an ultrasonic wave. The transducer senses the reflected wave and transmits the corresponding signal to transceiver circuitry that analyzes the incoming signal and generates an image signal that is shown on a display. In this manner, a user can see, on a monitor, a real-time image of a small portion of the interior surface of the heart. Repositioning or reorienting the catheter, such that the transducer's wave bounces off a different portion of the surface, will yield a new image.
The ICE technique has lacked the ability to link the ultrasound information with other clinical information such as cardiac electrographic data anatomic orientation of the ultrasound data or images.
Further, Wittkampf, in a series of patents (U.S. Pat. No. 5,983,126, issued Nov. 9, 1999; U.S. Pat. No. 5,697,377, issued Dec. 16, 1997), describes the application of orthogonal current pulses to an electrode arrangement on a catheter to yield three-dimensional position data to assist a user in navigating the catheter. More specifically, in the Wittkampf system, current pulses are applied to orthogonally placed patch electrodes placed on the surface of the patient. These patches are used to create specific electric fields inside the patient. The Wittkampf patents teach the delivery of small-amplitude low-current pulses supplied continuously at three different frequencies, one on each axis. Any measurement electrode placed in these electric fields experience a voltage that depends on its location between the various patches or surface electrodes on each axis. The voltage on the measurement electrode in the field when referred to a stable positional reference electrode indicates the position of the measurement electrode with respect to that reference. The three voltages give rise to a location of the measurement electrode in “three space”.
Co-pending application Ser. No. 10/819,027 describes the application of the Wittkampf technique, with improvements, to locate a catheter positioned in the interior of the heart and to image a catheter in real time. Further, application Ser. No. 10/819,027 describes how to sequentially use locations of an electrode in contact with the heart wall to sequentially build a model of a heart chamber.
Devices and techniques are known for determining the location in space and the orientation of the tip of a catheter. A series of patents to Desai (U.S. Pat. No. 5,215,103, issued Jun. 1, 1993; U.S. Pat. No. 5,231,995, issued Aug. 3, 1993; U.S. Pat. No. 5,397,339, issued Mar. 14, 1995; U.S. Pat. No. 4,940,064, issued Jul. 10, 1990; and U.S. Pat. No. 5,500,011, issued Mar. 19, 1996), incorporated herein by reference in their entirety, describes an electrode array arrangement located on a catheter that can be used to determine the location of the catheter tip using Wittkampfs technique.
What has been needed is a device and method for producing images of the interior of a heart via ultrasound coupled with a navigational system for allowing the user to see what portion of the heart is appearing on the ultrasound image. Further, what has been needed is a method for building a geometry of the heart by successively imaging portions of the heart surface, with successive images being framed based the location of the frames previously taken and by corresponding manipulation of the imaging device to select a new frame.